A major new finding about frogs came as a complete surprise to scientists who were trying to understand how its tongue and saliva worked to catch prey.
The frog is certainly one of the most unique species on the planet with its ability to snatch insects with its sticky tongue in a fraction of a second, but a new discovery by scientists shows just how unique this creature really is. Researchers found that the saliva of the frog essentially acts as a non-Newtonian fluid, functioning as both as a liquid and a solid at the same time, enabling the frog to catch insects or small animals with amazing speed.
Their saliva has a snot-like consistency, attaching to the prey and allowing the frog to pull it back into their mouth at a force that is 12 times stronger than gravity, and enabling the frog to grab prey that is 1.4 times their own body weight. Nothing humans have ever created can equal that.
What is a non-Newtonian fluid? Corn starch mixed with water is a good example. It flows like a liquid, but turns solid when you push on it. Frog saliva works the opposite way, however, turning to a liquid when it connects with the prey, but then filling in the cracks and crevices of the victim and solidifying in order to trap it.
“Frogs can capture insects, mice and even birds using only their tongue, with a speed and versatility unmatched in the world of synthetic materials,” the abstract states. “How can the frog tongue be so sticky? In this combined experimental and theoretical study, we perform a series of high-speed films, material tests on the tongue, and rheological tests of the frog saliva. We show that the tongue’s unique stickiness results from a combination of a soft, viscoelastic tongue coupled with non-Newtonian saliva. The tongue acts like a car’s shock absorber during insect capture, absorbing energy and so preventing separation from the insect. The shear-thinning saliva spreads over the insect during impact, grips it firmly during tongue retraction, and slides off during swallowing. This combination of properties gives the tongue 50 times greater work of adhesion than known synthetic polymer materials such as the sticky-hand toy. These principles may inspire the design of reversible adhesives for high-speed application.”